I purchased a load of fiberglass from an eBay seller last week. It came in today, but its pretty wrinkled. The wrinkles don't go away unless I really pull it tight. I'm making custom body panels with this stuff, so am I going to have to iron it before I apply it to the mold?

By the way, the fiberglass was 80 cents per running yard, 50" wide, 4 oz, and the guy has alot more if anyone is looking to buy some fiberglass for cheap. His eBay ID is avohio.

Is it woven cloth or random fiber mat? I don't have a concept of what 'wrinkled' means. If it is tightly creased wrinkles, this will severely weaken the strength of the cloth. After all it is just glass and dowsn't like being bent. If it is just mild waves, no problem. Regardless, the 'body' of this material is artificially applied by a resin soluble binder so the cloth should calm down when you soak it with the resin. Try a test with a small piece but I am pretty sure it won't cause you any problems once it is wet.

First off, its woven cloth. I'm not worried about any structural defects here. The glass strands aren't broken by any means. Imagine crumpling a wet shirt up, throwing it on the floor, and then picking it up a week later. Its that kind of wrinkled.

I'm just afraid that the wrinkles are going to show throw once the epoxy has been applied.

I can't imagine there being any kind of structual problem. Willys, do you really think so? I mean the fiberglass strands don't get "broken" unless you were to just smash it with a hammer or something.

A pack of fiberglass cloth for instance will be tightly folded into a "bolt" without any damage.

Psionic, as mitmaks said, it will layout flat once it is wet without a problem, it is designed to fit very tight contours and will with ease once dipped in resin. Of course if you were making an item with seriously important strength concerns like a drag boat hull or something you would want to have everything perfect.

But Willy's may have more experiance with the stuff and you should wait until he comes back with a yea or nay.

What are you making?

I just noticed you are going to be putting this cloth in epoxy. I would still think it would lay down. But being epoxy is so much thicker, it may not lay down as nice as the regular polyester fiberglass resin.

No, normally folded cloth isn't damaged but as I stated, I can't imagine what caused the 'wrinkled' cloth enough to worry about it affecting the lay. Cloth can be damaged if it is 'kinked'. If the part is not highly stressed, reconsider using epoxy for it. For one thing it will cost a bunch more with no real benefit over polyester and second, normal glass cloth is formulated for polyester resin that dissolves the binders whereas epoxy won't which makes layup harder to do and cloth wetting is not as efficient.

For any normal street/strip car part I can think of, polyester would be my choice.

Also, you need at least one layer of random thread fiberglass mat between your gel coat and the cloth. If you put the cloth on as the first layer under the gel coat the pattern of the cloth will print through no matter how much you sand and polish. The mat isolates the cloth weave pattern from the surface and allows a smooth surface.

I'm making a custom front bumper, rear bumper, fenders, and hood with the fiberglass. To be honest, the only reason I've chosen epoxy is because friends have told me to "do it right" and "just use epoxy". I haven't purchased any yet, but now I think I'm going to reconsider.

Also, about the gel coat, I would like someone to clear things up for me:

1) You spray gel coat on the mold to cover up defects and create a smooth surface on which you can layer your fiberglass.

2) You spray gel coat on the final part to create a smooth surface.

3) Gel coat is just another name for a resin.

4) Gel coating isn't nessecary if your mold is smooth enough.

A buddy of mine made a canoe out of kevlar. He made his mold out of wood, sanded it until it was super smooth, and layed 2 layers of kevlar and epoxy in it. The canoe is as perfectly smooth, strong and flexible enough.

Can someone point out what the visual and structural differences will be between a part that was gel coated, and a part that wasn't?

Also can someone point out where to get this stuff? I get most of my stuff from eBay, not much in the way of gel coating there.

Ok, I don't know a darn thing about using epoxy as a resin in a "fiberglass" componant. Barry, can you clear something up for me? I have been around a lot of fiberglass Rod body manufacturing, architectural manufacturing (come on now guys, you don't really think that ornate new building in town is really granite did you? ) , and the like, I have never seen epoxy used.

It makes sense that it would be stronger, but is it really being used in boats? I use to service a pretty high end boat repair shop in the Sacramento delta and all the boats appeared to be regular old polyester resin glass and the repairs seem to be made in regular old polyester resin. These were BIG buck yachts. Could these have been epoxy and I just don't know what I am looking at? Is the epoxy used for such a project different in appearance than the dark gray,white, blackish opaque looking resin we see in other epoxy products like adhesives?

And for goodness sakes, how the heck to you spell it "mould or Mold"????

Psionic, I am miles from being a glass expert but I would like to take a stab at your questions.

1. The gel coat isn't to cover up defects in the mould, but to "cover up" defects in the surface of piece you are making in the mould. When the glass is laid in the mould, if there are any air bubbles or flaws where you can't get the glass tucked into a nook or cranny the gel coat covers it up. There may be this void under the gel coat in the glass but you don't see it.
Willy's, Barry? At least that is what it looks like it is used for in production parts.

2 I have never seen gel coat sprayed after the part is pulled other than to repair something.

3. It isn't another name for resin,but it is made largely from resin. Resin and pigment color. Barry, Willy's , maybe some "talc" for body?

4. I imagine you are correct, but I have never seen a company make anything where it wasn't used. Those "carbon fiber" (something makes me doubt it really is carbon fiber) hoods you see on the little ricy cars, they have a clear gel coat I believe.

I don't think the smoothness of the mould is as critical as the smoothness of the application of mat, cloth and resin into the mould. If you don't get it down smooth, into every nook and cranny, pressing out every single bit of air bubbles and so on, you will have flaws in the outer surface of the part you pull out of the mould.

The "visual" difference is the part looks "painted" when pulled out of the mould if it is gel coated. MUCH better surface other paint products if you plan on painting it an automotive paint later.

"Structual"? I don't think one single iota.

The manufacture really uses the gel coat for a number of reasons, one is to insure the part will be smooth and free of defects. The other is what I just mentioned, it is already painted!

Here is little riddle you can ask your buddies.

What is painted before it even exists? A fiberglass boat!

Yep, before it is even made, it doesn't exist, the gel coat is sprayed in the mould. Thus it is "painted" before it even exists.

I just looked "mould, mold" up in the dictionary and found both are correct! I will be using "mold" from now on, one less letter to type.

Well, I have to agree with Martin on this one. We have a big named boat builder here in town and he uses nothing but polyester and mostly a chopper bun instead of cloth! And he builds speed boats the same way as fishing boats. Never have seen him use epoxy. I have never used it and in all my reading it is reserved for things like stress-skin race car bodies, aircraft parts and those funny car bodies that go 350mph and weigh 3oz! No doubt about it, epoxy reinforced carbon fiber is bullet proof.

Now about gel coat. Polyester resin used in laminating the cloth hardens very hard. It is a bear to finish for that reason. On the other hand, gel coat is formulated to be thixotropic - means thick coats stick on vertical surfaces - and it cures to the consistency of sanding primer. A gel coated surface can be treated exactly as you do a layer of PPG K36. If you want a perfect finish on a 'glass part, it must be gel coated. It has the added benefit of carrying permanent color so as Martin says, boat builders spray their color scheme in gel coat into a boat mold, lay in the fiberglass and pop out a perfectly finished boat shell needing no further finishing.

There are various grades of gel coat for various purposes. One is a tooling gel which is usually bright orange and is used to coat the inside surface of a fiberglass mold so it can produce many parts without damage to the valuable surface. Here are a few snap shot of a part I made recently showing;

a prototype made of wood plaster, whatever

The part finshed, painted and polished to perfection so I can get a perfect mold from it

The fiberglass mold finished inside with tooling gel and with parting lines so it can be taken off the part!

And finally the finished part with a thick white gel coat ready to finish sand and paint

Had to make the part in two pieces and epoxy it together.

I can tell from your questions you haven't read the educational sections of the web sites I linked above. Please do, they will answer a lot of your questions a lot better than I did. Fiberglast Co. sells how-to videos that are very informative. They also sell everything you need including the proper mold release agents, gel coats, resins and fabrics to do the job right. I buy all my stuff form them. I am a power ebaY user but I wouldn't buy my fiberglass materials there. WAY too much work involved to use inferior product and believe me there is a difference in quality in fiberglass materials.

On yachts?
Martin, maybe for inside repairs of non structural but not for transoms or holes??
Most likely if they bought it in 55 gallon drums it was an epoxy base.
I have seen Seado's repaired with polyester and small fiberglass boats.
Could well be?

Most major marine suppliers (industrial not your walk in stores) Don't even stock polyester in 55 gallon drums.

I guess thats why you west coats guys make a higher hourly rate
than us guys on the east coast- Your just better!!!
Maybe our water is different?

I don't get into fiberglass body cars but what are these guys using to mold the body's? They could use either but I would hope epoxy.

Not that this matters in the application being done here but I was in between coats of paint the first Time I got on.

Here are the main differences between epoxy resin and Polyester resin.
Polyester:
Dries faster
Less activator required.
Thinner bodied so easier to us on some parts.
Poor adhesion to wood and steel.
Fair adhesion to itself.
High in solvency so easy to have air bubbles.

Epoxy:
Heavy bodied less trapped air.
Dries slower
Requires higher strength activator (some 2:1, on high side)
Excellent adhesion to like product.
Excellent adhesion to wood.
Fair to good adhesion to metal.
30-60% more flexible.**
Less film (50%) to equal same strength.**
Higher heat tolerance.**

Now for the **:
There are different grade of epoxy fiberglass as it gets down to how much
Talc, chromium the manufacture ads to thicken up. If he uses cheaper heavy talc this will weaken the film and take away on flexibility and heat resistance.
If they blend with fine chromium or fine and medium grade talc of course it will be stronger.
Transoms are sandwiched in wood; this is why I would find it hard to believe
Any boat builder would use this, since polyester does not like to stick to wood.

I sell a boat builder and the smallest boat they make (all sea going) is 65Feet.
About 5 years ago an automotive paint warehouse special ordered 5- 55 gallon
Drums of polyester glass for a jobber selling to Martin/Lockheed they refused it because it was not epoxy and I thought I could help out and sell it for them to my boat builder.
He told me he had to sign an affidavit with the insurance company saying he would only use an epoxy.

Hmm. All the car builder and boat builders I am familiar with use good old polyester! Like I stated above I am pretty sure that the funny car, aircraft, and Indy guys use epoxy and exotic materials like carbon fiber and aramid because they need the superior physical properties. For plain vanilla car parts (I am pretty sure you will find every kit car on the market is polyester), good old smelly polyester is the ticket.

I know aviation has to because the Polyester will not hold up to the hydraulic fluid but today on out side of plane I have no clue if they even use fiberglass any more.

I would like to know about about the people building these 32 and 34 ford body's and others. Polyester being so brittle there would be an advantage.
Speedboats? last i knew (years ago) 80mph was the cut off for a polyester as well as most paints.

I think if you call the guy repairing holes in the big boats, he not using the polyester for that application, The adhesion and strength is just not there when your 20 miles out.

That could be true and makes sense for repairs on boats to use epoxy. Plenty of extra strength and small repairs materials would be cheap. I do know for sure that they use polyester for the new stuff. All the fiberglass supply sites I linked above suggest polyester repairs and polyester gel coat instead of paint for repairing boat holes. And when you start getting over 80mph, that kinda leaves 99% of the boaters behind! That starts getting into the high performance realm which starts begging for epoxy.

Car bodies do very well w/ polyester if the bracing is properly designed. I built the one piece, tilt hood of my Willys from polyester/mat, no cloth form a 'glass mold I too from the original hood (photos of it in my journal) and it is 15 years old and still going strong. A few small cracks but that looks authentic 60s gasser so I leave them there!

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.

User Name:

Password

Please enter a password for your user account. Note that passwords are case-sensitive.

Password:

Confirm Password:

Email Address

Please enter a valid email address for yourself.

Email Address:

Log-in

User Name

Remember Me?

Password

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.